Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
  • C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
  • C08F297/04—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising vinyl aromatic monomers and conjugated dienes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
  • C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
  • C08F297/04—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising vinyl aromatic monomers and conjugated dienes
  • C08F297/044—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising vinyl aromatic monomers and conjugated dienes using a coupling agent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/42—Introducing metal atoms or metal-containing groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
  • C08L53/025—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes modified

Definitions

• This invention relates to a process for making a coupled block copolymer composition and the resulting composition. More in particular, the invention relates to the coupling of anionic polymers and to the hydrogenation of such coupled polymers to make a polymer composition containing low levels of uncoupled polymer and having a substantial linear character.
• the coupling of lithium-terminated polymers is a process known in the art.
• a lithium-terminated polymer is treated with a compound having two or more reactive sites capable of reacting with the carbon- lithium bonds of the lithium-terminated polymer.
• the multifunctional coupling agent thereby becomes a nucleus for the resulting structure. From this nucleus long chain polymeric branches radiate and such coupled polymers have specific properties that render them useful for particular applications.
• Linear polymers are formed by employing coupling agents having two reactive sites.
• one coupling agent employed in making linear polymers is methyl benzoate as disclosed in
• Radial polymers are formed by employing coupling agents having more than two reactive sites.
• coupling agents include among others silica compounds, including silicon tetrachloride and alkoxy silanes (cf.
• polyepoxides polyisocyanates
• polyimines polyaldehydes, polyketones, polyanhydrides, polyesters, polyhalides (cf.
• the present invention broadly encompasses a process for making a coupled block copolymer composition, comprising the steps of: a. reacting a living lithium-terminated polymer having the formula P-Li, where P is a copolymer chain having at least one polymer block A composed of one or more mono alkenyl arenes having 8 to 18 carbon atoms and at least one polymer block B composed of one or more conjugated dienes having 4 to 12 carbon atoms, with an alkoxy silane coupling agent having the formula R-Si-(OR') , where R is selected from aryl radicals having from 6 to 12 carbon atoms, or linear alkyl and branched alkyl radicals having from 1 to 12 carbon atoms, and R' is selected from linear alkyl radicals having from 1 to 4 carbon atoms, and where the molar ratio of Si to Li is between 0.35 and 0.7, thereby forming a coupled block copolymer composition; b. optionally hydrogenating the coupled block
• the present invention also encompasses the resulting (hydrogenated) block copolymer compositions made using the alkoxy silanes of the process.
• the present invention includes a block copolymer composition comprising: a. a tetra-branched block copolymer (TV) represented by the general formula (P) X; b. a tri-branched block copolymer (EH) represented by the general formula (P) X; c. a di-branched block copolymer (H) represented by the general formula (P) X; and d.
• the present invention is a process which includes a step of reacting a living lithium-terminated polymer having the formula P-Li where P is a block copolymer chain of one or more conjugated dienes having 4 to 12 carbon atoms and one or more mono alkenyl arenes having 8 to 18 carbon atoms with the alkoxy silane coupling agent.
• the preferred acyclic conjugated dienes that can be polymerized into the polymer chain P of the present invention are those containing 4 to 8 carbon atoms.
• Examples for such conjugated dienes arel,3-butadiene (termed “butadiene” in the claims and elsewhere in the specification), 2,3-dimethyl-l,3butadiene, piperylene, 3-butyl-l,3-octadiene, isoprene, 2-phenyl-l,3-butadiene.
• Mono alkenyl arenes that can be polymerized together with the dienes to form the polymer chain P are preferably those selected from the group of styrene, the methylstyrenes, particularly 3-methylstyrene, the propylstyrenes, particularly 4-propylstyrene, the butyl styrenes, particularly p-t-butylstyrene, vinylnapthalene, particularly 1-vinylnapthalene, cyclohexylstyrenes, particularly 4-cyclohexylstyrene, p- tolylstyrene, and l-vinyl-5-hexylnaphthalene.
• the presently preferred monomers are isoprene, 1,3-butadiene and styrene.
• the presently preferred polymer chains P are those where the conjugated dienes are present in a major amount and the mono vinyl-substituted arenes are present in a minor amount. It is preferred that the mono alkenyl arene content be from 5 to 50 weight percent of the total block copolymer, more preferably from 10 to 35 weight percent.
• polymer chain P has a structure A-B- or B-A-A- or A-B-B'- so that B or
• B' is attached to the coupling agent, and in which A represents a block of mono alkenyl arenes, preferably a polystyrene block, and B and B' represent different blocks that confer rubbery properties to the polymer chain, such as a poly conjugated diene block, a copolymer block of a conjugated dienes, a copolymer block of a conjugated diene and a mono alkenyl-substituted arene (in which case the total content of mono alkenyl-substituted arene may be up to 70 weight percent), or a combination of such blocks.
• Such a polymer exhibits properties both of an elastomer and of a thermoplastic polymer. Therefore, such polymers can be formed into articles by standard procedures known for producing articles from thermoplastic polymers while the finished article exhibits elastomeric properties.
• the mono alkenyl-substituted are are present in a major amount, thus resulting in a polymer that exhibits the properties of a toughened polystyrene.
• the desired block weights are 3,000 to 60,000, preferably 5,000 to 50,000.
• the desired block weights are 20,000 to 200,000, preferably 20,000 to 150,000. These molecular weights are most accurately determined by light scattering measurements, and are expressed as number average molecular weights.
• the term "vinyl" has been used to describe the polymer product that is made when 1,3-butadiene is polymerized via a 1,2-addition mechanism.
• polymerized butadiene units should have 1,2-addition configuration.
• isoprene as the conjugated diene
• 5 to 80 mol percent of the polymerized isoprene units in the block have 3,4-addition configuration.
• Polymer microstructure mode of addition of the conjugated diene is effectively controlled by addition of an ether, such as diethyl ether, a diether, such as 1,2-diethoxypropane, or an amine as a microstructure modifier to the diluent. Suitable ratios of microstructure modifier to lithium polymer chain end are disclosed and taught in US RE27145E --.
• the quantity of coupling agent employed with respect to the quantity of living polymers P-Li present depends largely upon the degree of coupling and the properties of the coupled polymers desired.
• the coupling agent defined above will be employed in a range of from 0.35 to 0.7 moles of coupling agent per mole of lithium, P-Li, more preferably from 0.4 to 0.55 moles of coupling agent based upon the moles of lithium present in the polymer, P-Li, most preferably from 0.45 to 0.5 moles of coupling agent per mole of lithium, P-Li.
• Si/Li (mol/mol) ratios in excess of 0.7 are also not preferred.
• Si Li (mol/mol) 0.5
• Higher levels of Si/ Li (mol/mol) only result in the addition of excess coupling agent.
• the addition of excess reagent contributes added cost to the process without an advantage in the quality of the coupled polymer.
• the excess coupling agent will tend to cap living chain ends without linking them together; this will contribute to a decline in coupling efficiency at higher Si/Li molar ratios.
• Lower coupling efficiency will afford block copolymer products having less strength.
• the use of Si/Li (mol/mol) ratios in excess of 0.7 will unnecessarily increase the cost of the process and will afford lower quality coupled polymers.
• the coupling agent used in the present invention is an alkoxy silane of the general formula R -Si-(OR') , where R is selected from aryl, linear alkyl and x 3 branched alkyl radicals, and R' is selected from linear alkyl radicals.
• Preferred trialkoxy silanes are methyl trimethoxy silane ("MTMS”), methyl triethoxy silane (“MTES”), isobutyl trimethoxy silane (“IBTMO”) and phenyl trimethoxy silane (“PhTMO”). Of these the more preferred is methyl trimethoxy silane.
• the temperature at which the coupling reaction is carried out can vary over a broad range and, for convenience, often is the same as the temperature of polymerization. Although the temperature can vary broadly from 0° to 150°C, it will preferably be within the range from 30°C to 100°C, more preferably 55°C to 80°C.
• the coupling reaction is normally carried out by simply mixing the coupling agent, neat or in solution, with the living polymer solution.
• the reaction period is usually quite short, and can be affected by the mixing rate in the reactor.
• the normal duration of the coupling reaction will be in the range of 1 minute to 1 hour. Longer coupling periods may be required at lower temperatures.
• the linked polymers may be recovered, or if desired they may be subjected to hydrogenation, for instance, the selective hydrogenation of the diene portions of the polymer. Hydrogenation generally improves thermal stability, ultraviolet light stability, oxidative stability, and weatherability of the final polymer. It is important that the coupling agents not interfere with or otherwise "poison" the hy- drogenation catalyst.
• Hydrogenation can be carried out via any of the several hydrogenation or selective hydrogenation processes known in the prior art. For example, such hydrogenation has been accomplished using methods such as those taught in, for example, US 3595942 -.
• Such methods operate to hydrogenate polymers containing aromatic or ethylenic un- saturation, and are based upon operation of a suitable catalyst.
• a suitable catalyst preferably comprises a Group Vm metal such as nickel or cobalt which is combined with a suitable reducing agent such as an aluminum alkyl or hydride of a metal selected from Groups I- A, II-A and ⁇ i-B of the Periodic Table of the Elements, particularly lithium, magnesium or aluminum.
• a suitable solvent or diluent for instance at a temperature from 20°C to 100°C, and a pressure of 2 bars to 50 bars.
• Other catalysts that are useful include titanium based catalyst systems and various heterogeneous catalysts.
• Selective hydrogenation can be carried out under such conditions that at least 90 percent of the conjugated diene double bonds have been reduced, and between zero and 10 percent of the arene double bonds have been reduced. Preferred ranges are at least 95 percent of the conjugated diene double bonds have been reduced, and more preferably 98 percent of the conjugated diene double bonds are reduced.
• the ratio of alcohol to P-Li is from 0.05 to 1.5 moles of alcohol per mole of P-Li (where the amount of P-Li in the calculation is based on the amount of living chain ends which were present prior to the addition of the coupling agent).
• the hydrogenated polymers may be cleaned up by standard techniques, such as addition of aqueous acid solutions to remove the residues of the polymerization initiator and hydrogenation catalyst. It is usually preferred to add an antioxidant to the reaction mixture before isolation of polymer.
• the polymer may be separated from the reaction mixture by standard techniques, such as steam stripping or coagulation with a suitable non-solvent such as an alcohol or water.
• a suitable non-solvent such as an alcohol or water.
• the polymer crumb may be separated from the volatile solvent by countercurrent flow through a cyclone.
• the coagulated polymer crumb may be separated from the liquid solvent phase by cen- trifugation or filtration.
• the polymer may be recovered by passing the cement through a devolatilizing extruder. Residual solvent and other volatiles can be removed from the isolated polymer by heating, optionally under reduced pressure or in a forced airflow.
• the living polymer chain P-Li As far as the synthesis of the living polymer chain P-Li is concerned, this may be obtained by reacting a mono-functional lithium initiator system with the respective monomer or monomers. This polymerization step can be carried out in one step or in a sequence of steps. In the case where the polymer chain P comprises a random or tapered copolymer block of two or more monomers, the monomers may be simultaneously polymerized with the lithium initiator. In the case where the polymer chain P is a block copolymer comprising two or more homo- or copolymer blocks, these individual blocks can be generated by incremental or sequential monomer addition.
• the lithium-based initiator systems used to make the living polymer chain generally have the general formula R" Li wherein R" is a hydrocarbyl radical of 1 to 20 carbon atoms.
• R" is a hydrocarbyl radical of 1 to 20 carbon atoms.
• lithium initiators are methyllithium, isopropyllithium, n- butyllithium, sec-butyllithium, t-octyllithium, n-dodecyllithium, n-eicosyllithium, phenyllithium, naphthyllithium, p-tolyllithium, 4-phenylbutyllithium, cyclo- hexyllithium, and 4-cyclohexyllithium.
• the amount of the lithium initiator employed depends upon the desired properties of the polymer, particularly the desired molecular weight. Normally, the organomonolithium initiator is employed in the range of from 0.1 to 100 gram millimoles per 100 grams of total mono
• the polymerization reaction is preferably carried out in the presence of a hydrocarbon diluent.
• a hydrocarbon diluent is a paraffinic, cycloparaffinic or aromatic hydrocarbon having from 4 to 10 carbon atoms or a mixture of such diluents.
• the diluent are n-hexane, hexanes, n-heptane, heptanes, 2,2,4-trimethylpentane, cyclohexane, cyclopentane, isopentane, benzene and toluene.
• the reaction is generally carried out with a weight ratio of diluent to monomers exceeding 1.
• the diluent is employed in a quantity of from 200 to 1000 parts by weight per 100 parts by weight of total monomers.
• the polymerization reaction in step 1 usually occurs within a period of time ranging from a few minutes up to 6 hours. Preferably, the reaction is carried out within a time period of from 10 minutes to 2 hours.
• the polymerization temperature is not critical and will generally be in the range of from 30°C to 100°C, preferably in the range of 55° to 85° C.
• the other object of the present invention comprises coupled block copolymer compositions having substantial linear character.
• the relative amounts of the tetra-branched (TV), tri-branched (II), di-branched (II) and linear diblock (I) species are: 0 to 5 weight percent tetra-branched IV, 0 to 10 weight percent tri-branched HI, 65 to 95 weight percent di-branched II and 0 to 20 weight percent linear diblock I.
• Preferred amounts are: 0 to 3 weight percent IV, 0 to 8 weight percent m, 79 to 95 weight percent II and 0 to 10 weight percent I.
• the block copolymer composition has a Coupling Efficiency ("CE") of 80 to 98 weight percent, preferably 90 to 98 weight percent.
• Coupling Efficiency is defined as the proportion of polymer chain ends which were living, P-Li, at the time the coupling agent was added that are linked via the residue of the coupling agent at the completion of the coupling reaction.
• GPC Gel Permeation Chromatography
• E+III+IV The sum of the areas under the GPC curve for all of the coupled species (E+III+IV) is divided by the sum of the areas under the GPC curve for all of the coupled moieties plus the area under the curve for the starting, uncoupled polymer species (I+E+IE+IV). This ratio is multiplied by 100 to convert the coupling efficiency to a percentage value.
• styrene/butadiene block copolymers were prepared with a variety of coupling agents according to a standard polymerization recipe.
• the molecular parameters of the desired polymer is shown below in Table 1, where Step 1 is the polystyrene block (A), SD1 apparent is the styrene equivalent molecular weight of the styrene/butadiene diblock arm (P), and CE is coupling efficiency.
• Coupling Efficiency is defined as the proportion of polymer chain ends which were living, P-Li, at the time the coupling agent was added that are now linked via the residue of the coupling agent at the completion of the coupling reaction.
• GPC Gel Permeation Chromatography
• the butadiene polymerization was started at 70°C and the temperature was raised adiabatically up to 80°C. After the butadiene addition was stopped, a soak time of 5 minutes was maintained. Following that the coupling agent was added and allowed to react for at least 10 minutes before the polymer cement was sampled.
• TMS Trimethoxy silane hydride

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